Automatic re-authentication

1. A server system programmed to perform actions comprising: authenticating a client device for a particular server session; sharing auto-reconnect data with the client device, the auto-reconnect data including a session ID associated with the particular server session and a first random number; after losing communications with the client device, sharing a second random number with the client device, and receiving from the client device the session ID and a session verifier that is derived at least in part from the first and second random numbers; validating the session verifier; upon successfully validating the session verifier, automatically re-authenticating the client device for the particular server session.

2. A server system as recited in claim 1 , wherein said re-authenticating is performed without requesting user credentials.

3. A server system as recited in claim 1 , wherein said sharing auto-reconnect data is performed through a secure data communications channel.

4. A server system as recited in claim 1 , wherein automatically re-authenticating the client device for the particular server session includes automatically re-authenticating the client device based at least partially on the session ID.

5. A server system as recited in claim 1 , wherein the session verifier comprises a one-way hash based at least in part on the first and second random numbers.

6. A server system as recited in claim 1 , wherein said actions further comprise periodically changing at least a portion of the auto-reconnect data and sending at least said changed portion to the client device.

7. A server system as recited in claim 1 , further comprising periodically changing the first random number and sending it to the client device.

8. A client device programmed to perform actions comprising: providing user credentials to a server system to authenticate the client device with the server system; initiating a server session on a server system, the server session being associated with the client device; sharing auto-reconnect data with the server system, the auto-reconnect data including a session ID and a first random number; after losing and re-establishing communications with the server system, sharing a second random number with the server system, and deriving a session verifier at least in part from the first and second random numbers; requesting automatic re-authentication by the server system without providing user credentials, wherein said requesting comprises sending the session ID and the session verifier to the server system.

9. A client device as recited in claim 8 , wherein said actions further comprise periodically sharing a changed first random number with the server system.

10. A client device as recited in claim 8 , wherein the auto-reconnect data is received from the server system.

11. A methods comprising: establishing data communications between a client device and a server system; authenticating the client device for a particular server session; sharing auto-reconnect data between client device and the server system, the auto-reconnect data including a session ID associated with the particular server session and a first random number; re-establishing data communications between the client device and the server system after a communications failure; after re-establishing data communications, sharing a second random number between the client device and the server device; deriving a client session verifier at the client device at least in part from the first and second random numbers; providing the client session verifier and the session ID from the client device to the server system; deriving a server session verifier at the server system at least in part from the first and second random numbers; validating the client session verifier by comparing it to the server session verifier; upon successfully validating the session verifier, automatically re-authenticating the client device for the particular server session.

12. A method as recited in claim 11 , wherein the client session verifier and server session verifier comprise a one-way hash based at least in part on the first and second random numbers.

13. A method as recited in claim 11 , further comprising periodically changing at least a portion of the auto-reconnect data and sharing at least said changed portion between the client device and the server device.

14. A method as recited in claim 11 , further comprising periodically changing the first random number and sharing it between the client device and the server device.